<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div id="app">
    <div>
      <p>请选择你要购买的书籍</p>
      <ul>
        <li v-for="(item, index) in arr":key="index">
            {{item.name}} <button @click.prevent="add(index)">买书</button>
        </li>
      </ul>
      <table border="1" width="500" cellspacing="0">
        <tr>
          <th>序号</th>
          <th>书名</th>
          <th>单价</th>
          <th>数量</th>
          <th>合计</th>
        </tr>
        <tr v-for="(item, index) in arr">
            <td>{{index+1}}</td>
            <td>{{item.name}}</td>
            <td>{{item.price}}</td>
            <td>{{item.count}}</td>
            <td>{{item.price * item.count}}</td>
        </tr>
      </table>
      <p>总价格为: {{totalPrice}} </p>
    </div>
  </div>
  <script src="./vue.js"></script>
  <script>
    // 目标: 把数据铺设到页面上, 当用户点击买书按钮, 书籍数量增加1, 并且要计算累计的和
    const app = new Vue({
      el: '#app',
      data: {
        arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
      },
      computed: {
        totalPrice() {
            return this.arr.reduce((sum, item) => sum + item.price * item.count,0)
        }
      },
      methods: {
        add (index) {
            this.arr[index].count++
        }
      }
    })
  </script>
</body>

</html>